The present invention relates to aircraft brake piston adjuster assemblies, and in particular to an aircraft brake piston hydraulic adjuster assembly.
External, non-concentric aircraft brake piston adjusters in multidisc aircraft brakes are located in the piston housing at positions circumferentially between the pistons, and transmit piston return loads through the first brake disc which is generally referred to as the "pressure plate". The return loads of such adjusters tend to distort the pressure plate, can decrease the uniformity of the distribution of brake actuation pressure during braking, and tend to increase heat transfer from the heat sink to the pistons because the pistons are continuously in contact with the pressure plate. Prior concentric piston adjusters are located within the pistons and retract the pistons away from the brake heat sink to thereby eliminate the disadvantages of external adjusters. Such internal concentric adjusters are anchored to the brake structure by a pin inserted in a sealed gland in the piston dome. During brake actuation, structural deformations and vibrations tend to cause internal adjuster parts to chafe and wear, which often leads to adjuster pin leakage and desultory failures of adjuster components.
It is highly desirable to provide a brake piston adjuster assembly which eliminates the adjuster pin and seal, and which comprises fewer parts and no small parts. It is preferable that as much as possible of the brake piston adjuster assembly be stationery relative to the piston housing so that it is less subject to vibrations from the heat sink. It is highly desirable to provide a brake piston adjuster assembly which automatically adjusts the return position of the brake piston as the brake friction surfaces of the discs wear. It is considered advantageous if the adjuster assembly does not include any permanently deforming parts and does not rely on mechanical friction loads, which are difficult to maintain with consistent accuracy, to obtain the adjustment feature. It is desirable that, when the landing gear is retracted and the brake is oriented vertically, the adjustment feature prevents the weight of the brake friction discs from pushing the brake piston back into the housing. It is desirable that hydraulic fluid utilized for the adjustment feature be easily released when the brake piston is reset during overhaul.